The invention relates to an arrangement for generating shock waves and, more particularly, to an arrangement having two two-dimensional shock wave sources which focus onto a point in a non-geometric sense, or an overlapping area. Shock waves as used in this context also include weak acoustic pressure pulses having an intensity which however, is sufficient for causing changes in the bodies of living beings. For example, shock waves allowing for the moving of stones or the heating of the tissue.
A lithotrite having a two-dimensional source is known from German Patent Document DE-OS 31 19 295. This 2-D source is constructed to be self focussing either as a calotte shell or flat. For focussing, imaging systems are then required, such as reflectors, lenses or electric controls of the different zones of the shock wave source.
From German Utility Model Document DE-Gm 88 02 995, a lithotrite is known which has two shock wave sources. On the one hand, shock waves are generated outside the body and are guided to the stone through the skin. On the other hand, the shock waves are generated at the end of a light guide in the proximity of the stone.
From European Patent Document EP 277 489 A, a lithotrity working area is known which has two shock wave sources which are independent of one another and which affect the stone from different directions. This arrangement is described above.
It has also been suggested from German Patent Application P 38 33 862 to combine a punctiform and a two-dimensional shock wave source with one another.
There is therefore needed an arrangement which improves the fragmentation of human concrements, particularly of gallstones.
According to the present invention, this need is met by an arrangement having two two-dimensional shock wave sources focussing onto a point or an overlapping area wherein the shock wave sources are of different types.
The arrangement is characterized in that one of the first and second shock wave sources is an electromagnetic shock wave source, and the other shock wave source is a piezoelectric shock wave source. The first and second shock wave sources are arranged coaxially, with the electromagnetic shock wave source arranged on the inside, and the piezoelectric shock wave source arranged on the outside surrounding the electromagnetic shock wave source. The arrangement further comprises a pulse circuit for feeding the first and second shock wave sources.
The use of two different types of shock wave sources offers the advantages of both types individually so long as both sources are operated independently of one another. These advantages include the free selection of the energy or the size of the focus. When both sources are operated in a combined manner, particularly controlled by a pulse circuit with a settable time delay, additional advantages are achieved. As a result of the variable time-related superposition of shock waves having different characteristics such as different energy densities, varying tension wave proportion, different focus sizes, etc. special effects may occur on a stone that was already stimulated by the other source.
Preferably, a piezo-system and an electromagnetic shock wave system are used. In this case, both systems may be self-focussing, e.g., arranged on a curved carrier or flat. The focussing then takes place by means of auxiliary devices, such as lenses, reflectors, or electronically by means of the differing control of the individual zones of the shock wave sources. Specifically, the two mentioned sources can easily be synchronized with respect to time.
The preferred coaxial arrangement leaves unchanged the expenditures with respect to the locating and positioning in comparison to a single source. An arrangement of the sources next to one another (not shown) is also possible.
It is advantageous to provide the coaxial arrangement of an electromagnetic source (EMSE) on the inside and of a piezoelectric source on the outside because the larger area is then available to the source with the lower energy density. The electromagnetic source may be self-focussing or may be focussed by means of a lens. The piezoelements are preferably arranged in a self-focussing manner on a spherical carrier.
A defined time delay between the two shock wave sources can be set electrically when one pulse circuit is used for both sources or by means of a mechanical adjustment of the sources with respect to one another by way of the operating time which will then be different.
If one of the systems is a piezo-system, target control can also be carried out by means of the combination system. In this case, the reflexes of the shock wave pulses of one partial shock source on the stone are detected by the other partial shock source.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.